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Modelação Numérica do Processo de Escavação e Execução de Contenção Periférica em Meio Urbano Considerando a Rigidez do Solo na Gama das Pequenas Deformações
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Advisor(s)
Abstract(s)
Nos grandes centros metropolitanos, comumente são executadas obras com forte componente
geotécnica, caracterizadas pela ocupação do terreno até profundidades relativamente elevadas. As
estruturas de contenção flexíveis, utilizadas para suporte do terreno, sofrem em serviço deformações
que condicionam a grandeza e distribuição dos impulsos sobre si. Para análise do comportamento destas
estruturas, existem ferramentas que simulam, de forma aproximada, o comportamento em obra,
auxiliando na garantia da segurança dos edifícios vizinhos e própria estrutura.
Nesta tese, pretendeu-se analisar a importância da caraterização da rigidez do solo na gama das muito
pequenas deformações e impacto da consideração deste parâmetro em modelos de elementos finitos,
utilizados para previsão dos deslocamentos de uma cortina de estacas moldadas, executada para a
construção de um edifício em Lisboa.
Para isso, inicialmente procurou-se compreender de que forma o software PLAXIS modela o solo na
gama das muito pequenas deformações, utilizando o modelo constitutivo Hardening Soil Small-Strain
Stiffness (HSsmall). Para melhor compreensão deste modelo, foram simulados ensaios triaxiais, no
PLAXIS, considerando os modelos HSsmall, Hardening Soil (HS) e Mohr-Coulomb (MC), e
comparados os resultados obtidos.
O caso de estudo é constituído por uma contenção periférica construída para implantação dum edifício
no centro de Lisboa, constituído por 17 pisos elevados e 6 enterrados. A construção desta estrutura foi
simulada no mesmo software, considerando os modelos HS e HSsmall. Para tal, foi fundamental a
aferição dos parâmetros de rigidez do terreno, recorrendo a ensaios in situ geofísicos e resultados de
ensaios de penetração. Assim, verificou-se que os deslocamentos obtidos considerando a rigidez na
gama das muito pequenas deformações e aplicando o modelo HSsmall, aproximaram-se mais dos
deslocamentos aferidos em obra. Os deslocamentos obtidos com o modelo HS e contemplando valores
de rigidez determinados baseados em ensaios SPT, foram significativamente superiores aos registados
em obra, logo após a conclusão da escavação.
In large metropolitan centers, construction works with a strong geotechnical component are commonly carried out, characterized by the occupation of the land to relatively high depths. Flexible retaining structures, used to support the soil, experience in service deformations that condition the magnitude and distribution of the earth pressure on themselves. To analyse the behaviour of these structures, there are tools that allow simulating, in an approximate way, the behaviour on site, helping to ensure the safety of neighbouring buildings and the structure itself. In this thesis, we analyse the results of soil characterization, in the range of very small deformations, with the purpose of estimating more realistically the displacements of a bored pile wall executed for the construction of a building in Lisbon. For this, the first step was to understand how the PLAXIS software models soil behaviour in the range of very small deformations, using the constitutive model Hardening Soil Small-Strain Stiffness (HSsmall). For an understanding of this model, triaxial tests were simulated in PLAXIS, considering the HSsmall, Hardening Soil (HS) and Mohr-Coulomb (MC) models, and the results were compared. The case study consists of a deep excavation with bored pile wall, made for the implantation of a building in the center of Lisbon, with 17 raised floors and 6 buried. The construction of this structure was simulated in the same FEM software, considering the models HS and HSsmall. For this purpose, soil stiffness estimated based on penetration tests and seismic tests were used, respectively. In this case, the displacements obtained considering small strain stiffness and using the HSsmall model were closer to the displacements measured on-site. The displacements obtained with the HS model and considering soil stiffness estimated based on SPT test results, were significantly higher than the ones measured, shortly after the end of the excavation process.
In large metropolitan centers, construction works with a strong geotechnical component are commonly carried out, characterized by the occupation of the land to relatively high depths. Flexible retaining structures, used to support the soil, experience in service deformations that condition the magnitude and distribution of the earth pressure on themselves. To analyse the behaviour of these structures, there are tools that allow simulating, in an approximate way, the behaviour on site, helping to ensure the safety of neighbouring buildings and the structure itself. In this thesis, we analyse the results of soil characterization, in the range of very small deformations, with the purpose of estimating more realistically the displacements of a bored pile wall executed for the construction of a building in Lisbon. For this, the first step was to understand how the PLAXIS software models soil behaviour in the range of very small deformations, using the constitutive model Hardening Soil Small-Strain Stiffness (HSsmall). For an understanding of this model, triaxial tests were simulated in PLAXIS, considering the HSsmall, Hardening Soil (HS) and Mohr-Coulomb (MC) models, and the results were compared. The case study consists of a deep excavation with bored pile wall, made for the implantation of a building in the center of Lisbon, with 17 raised floors and 6 buried. The construction of this structure was simulated in the same FEM software, considering the models HS and HSsmall. For this purpose, soil stiffness estimated based on penetration tests and seismic tests were used, respectively. In this case, the displacements obtained considering small strain stiffness and using the HSsmall model were closer to the displacements measured on-site. The displacements obtained with the HS model and considering soil stiffness estimated based on SPT test results, were significantly higher than the ones measured, shortly after the end of the excavation process.
Description
Keywords
Comportamento não-linear dos solos Elementos finitos Estruturas de contenção flexíveis Gama das muito pequenas deformações Modelação numérica Non-linear behavior of soils Finite elements Flexible retaining structures Range of very small deformations Numerical modelling . Engenharia Civil